A systematic review of nomograms used in urolithiasis practice to predict clinical outcomes in paediatric patients

Predictive value of scoring systems for stone free status and complications before percutaneous nephrolithotomy in children

PCNL, a minimally invasive surgical technique for kidney stone removal, relies on achieving stone-free status, which various scoring systems aim to predict. This study assesses the predictive accuracy of the Clinical Research Office of the Endourological Society (CROES) and Guy's Stone Score (GSS) systems in determining stone-free rates following percutaneous nephrolithotomy (PCNL) in pediatric patients. A retrospective analysis was conducted on 580 pediatric patients who underwent PCNL at Çukurova University Urology Clinic between January 2007 and March 2024. Patients were categorized into two groups based on postoperative stone status: Group 1 and Group 2. CROES and GSS scores were calculated for each patient. The association between these scores and stone-free status, as well as postoperative complications, was statistically analyzed. Additionally, subgroup analyses were performed based on age groups. The study showed that 83.7% of patients achieved a stone-free condition postoperatively. Significant differences were found between the stone-free and residual stone groups regarding stone burden and operative time (p < 0.001). CROES had high accuracy for predicting stone-free outcomes (p < 0.001), while GSS was also effective in predicting both stone-free rates and complications. CROES was less effective in predicting complications. Both CROES and GSS are valuable for predicting PCNL outcomes in pediatric patients. While CROES is more reliable for stone-free rates, GSS better predicts complications. However, their limitations highlight the need for pediatric-specific scoring models. Until such models are developed, these systems should be used with caution alongside individualized clinical assessments.

"Development and validation towards a Nomogram to predict acute kidney Injury following PCNL"

OBJECTIVES

To evaluate the occurrence, risk factors, and outcomes of post PCNL (Percutaneous Nephrolithotomy) Acute Kidney Injury (AKI), with a secondary goal of developing a nomogram for post-PCNL AKI prediction.

METHODS

A prospective observational study was conducted enrolling 333 patients who underwent PCNL between February 2022 and February 2023. Patient demographics, comorbidities, perioperative lab parameters, stone characteristics, intraoperative details, and postoperative AKI were assessed. Logistic regression analyses were employed to construct a nomogram for predicting post-PCNL AKI.

RESULTS

40 patients (12.4%) experienced postoperative AKI, with recovery observed in all cases during the 3-month follow-up. Female gender (p = 0.002), hypertension(p = 0.022), higher serum uric acid levels(p = 0.003), staghorn calculi(p = 0.001), higher Hounsfield Units(p = 0.013), bilateral PCNL(p < 0.001), larger tract size(p = 0.017), longer operative time(p < 0.001), greater stone volume(p = 0.025), higher baseline serum creatinine levels(p < 0.001), higher postoperative total leukocyte count(p = 0.005), and postoperative fever(p < 0.001) were significantly associated with the AKI group. Regression analysis identified female gender (OR = 0.26, p = 0.035), higher serum uric acid levels(OR = 1.62, p = 0.013), bilateral PCNL(OR = 12.55, p < 0.001), longer operation time(OR = 1.02, p = 0.047), and larger stone volume(OR = 1.12, p = 0.015) as independent risk factors for postoperative AKI. The internally validated nomogram(n = 70) for predicting AKI demonstrated excellent diagnostic performance, with an area under the ROC curve of 0.984(95% CI, p < 0.001).

CONCLUSION

AKI occurs in approximately 12% of patients undergoing PCNL. We identified several significant predictors of post-PCNL AKI, including female gender, hypertension, hyperuricemia, higher Hounsfield units, larger stone volume, bilateral PCNL, larger access tract size, and longer operative time. Awareness of these factors is crucial for optimizing management and improving patient outcomes.

Validation of stone-kidney size score to predict outcome and complications of pediatric percutaneous nephrolithotomy

INTRODUCTION

The prevelance of urinary system stone disease in children is emphasizing the need for minimally invasive treatments to decrease morbidity and recurrence risk. Percutaneous nephrolithotomy (PCNL) has emerged as a preferred approach for pediatric patients with complex stones due to its minimally invasive nature, including miniaturized and vacuum-assisted access sheaths, advanced laser technology and tubeless and outpatient procedures. However, adult scoring systems have proven ineffective in predicting success and complications in pediatric PCNL. This highlights the need for specialized scoring systems, such as the Stone-Kidney Size (SKS) scoring system, tailored to pediatric patients and will be evaluated in our study for its association with the stone-free rate (SFR) and complications.

MATERIALS AND METHODS

The data of 144 patients aged <17 years who had undergone PCNL between January 2008 and December 2019 were evaluated retrospectively. Demographics, stone characteristics, perioperative/postoperative outcomes were recorded for each patient. The SKS scoring system comprises the stone kidney index (SKI) and the number of stones, assigns one or two points based on single or multiple stones and an SKI value of <0.3 or ≥0.3, respectively. The SKI is computed by dividing the stone's longest axis by the kidney's longest axis. Residual stones less than 4 mm on non-contrast computed tomography are considered clinically insignificant residual fragments (CIRFs). Stone-free and CIRF patients were considered successful results. The relationship between the SKS scoring system and SFR, success, and complication rates after surgery was investigated. Statistical analyses were conducted using SPSS 22.0 software.

RESULTS

The SFR was 67.36% and 74.31% when CIRF patients were included, respectively, with a complication rate of 27%. In multivariate analysis, stone treatment history, stone burden, and SKS score were statistically significantly associated with SFR (p < 0.001, p = 0.032, p < 0.001, respectively). Furthermore, the SKS score was the only variable that showed a statistically significant relationship with success. No significant association was found between SKS score and complications (p = 0.342).

DISCUSSION

Our study demonstrates a relationship between the SKS scoring system and SFR in pediatric PCNL patients. However, shortcomings have been observed in its capacity to accurately predict post-PCNL complications. Despite being a retrospective analysis and having a single-center design, our study externally validates the relationship between the SKS scoring system and SFR after pediatric PCNL.

CONCLUSIONS

The SKS scoring system is associated with SFR in pediatric patients undergoing PCNL; however, this relationship has not been established for complications.

Stone-scoring systems for predicting complications in percutaneous nephrolithotomy: A systematic review of the literature

Objective

Percutaneous nephrolithotomy is a treatment of choice for larger stones of the upper urinary tract. Currently, several nephrolithometric nomograms for prediction of post-operative surgical outcomes have been proposed, although uncertainties still exist regarding their roles in the estimation of complications.

Methods

We conducted a systematic review on PubMed and Web of Sciences databases including English studies with at least 100 cases and published between January 2010 and December 2021. We identified original articles evaluating correlations between the Guy's stone score, the stone size (S), tract length (T), obstruction (O), number of involved calices (N), and essence or stone density (E) (S.T.O.N.E.), Clinical Research Office of the Endourological Society (CROES), and Seoul National University Renal Stone Complexity (S-ReSC) scores and post-operative complications in adult patients. We also included newly designed nomograms for prediction of specific complications.

Results

After an initial search of 549 abstracts, we finally included a total of 18 papers. Of them, 11 investigated traditional nephrolithometric nomograms, while seven newly designed nomograms were used to predict specific complications. Overall, 7316 patients have been involved. In total, 14 out of 18 papers are derived from retrospective single-center studies. Guy's stone score obtained correlation with complications in five, S.T.O.N.E. nephrolithometry score in four, while CROES score and S-ReSC score in three and two, respectively. None of the studies investigated minimally invasive percutaneous nephrolithotomy (PCNL) and all cases have been conducted in prone position. Considering newly designed nomograms, none of them is currently externally validated; five of them predict post-operative infections; the remaining two have been designed for thromboembolic events and urinary leakage.

Conclusion

This review presents all nomograms currently available in the PCNL field and highlights a certain number of concerns. Published data have appeared contradictory; more recent tools for prediction of post-operative complications are frequently based on small retrospective cohorts and lack external validations. Heterogeneity among studies has also been noticed. More rigorous validations are advisable in the future, involving larger prospective patients' series and with the comparison of different tools.